Prevalence and Population-Attributable Risk for Chronic Airflow Obstruction in a Large Multinational Study

Abstract

Rationale: The Global Burden of Disease program identified smoking and ambient and household air pollution as the main drivers of death and disability from chronic obstructive pulmonary disease (COPD). Objectives: To estimate the attributable risk of chronic airflow obstruction (CAO), a quantifiable characteristic of COPD, due to several risk factors. Methods: The Burden of Obstructive Lung Disease study is a cross-sectional study of adults, aged ≥40, in a globally distributed sample of 41 urban and rural sites. Based on data from 28,459 participants, we estimated the prevalence of CAO, defined as a postbronchodilator FEV₁-to-FVC ratio less than the lower limit of normal, and the relative risks associated with different risk factors. Local relative risks were estimated using a Bayesian hierarchical model borrowing information from across sites. From these relative risks and the prevalence of risk factors, we estimated local population attributable risks. Measurements and Main Results: The mean prevalence of CAO was 11.2% in men and 8.6% in women. The mean population attributable risk for smoking was 5.1% in men and 2.2% in women. The next most influential risk factors were poor education levels, working in a dusty job for ≥10 years, low body mass index, and a history of tuberculosis. The risk of CAO attributable to the different risk factors varied across sites. Conclusions: Although smoking remains the most important risk factor for CAO, in some areas, poor education, low body mass index, and passive smoking are of greater importance. Dusty occupations and tuberculosis are important risk factors at some sites.

Keywords: Burden of Obstructive Lung Disease (BOLD) study; chronic airflow obstruction; multinational study; population-attributable risk.

Figure 1.

Flow diagram showing recruitment to the study.

Figure 2.

Sex-specific relative risk for chronic airflow obstruction among 28,459 adults aged 40–89 years, and their variation across sites. The P value relates to the significance of the I-squared value. Square sizes reflect the amount of statistical information (i.e., inversely proportional to the variance of the log RR), together with the 95% credible intervals (horizontal lines) representing the Bayesian equivalent to the frequentist 95% confidence intervals. 95% CrI = 95% credible interval; RR = relative risk mutually adjusted for all risk factors shown here. *Reference: never-smoker; **reference: more than secondary school; ***reference: normal weight (18.5–24.9 kg/m²).

Figure 3.

Population-attributable risk (i.e., prevalence of chronic airflow obstruction attributable to different risk factors) by site for (A) men and (B) women.

Figure 3.

Population-attributable risk (i.e., prevalence of chronic airflow obstruction attributable to different risk factors) by site for (A) men and (B) women.